Killough, Ian – Homework 8 – Due: Nov 14 2006, 4:00 pm – Inst: Donna C Lyon
1
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printout
should
have
20
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
The due time is Central
time.
This
HW
assignment
is
due
Tuesday,
November 14, by 4:00PM.
001
(part 1 of 3) 10 points
Make the following assumptions:
1) The density of liquid water at 100
◦
C is 1.00
g/mL;
2) the vapor is adequately described by the
ideal gas equation;
3) the external pressure is constant at 1.00
atm; and
4) the heat of vaporization of water is 2.26
kJ/g.
What is
q
for the vaporization of 1.00 g of
liquid water at 1.00 atm and 100
◦
C, to the
formation of 1.00 g of steam at 1.00 atm and
100
◦
C?
1.
q
= 3
.
24 kJ
2.
q
= 0
.
126 kJ
3.
q
= 0 kJ
4.
q
= 1
.
67 kJ
5.
q
= 2
.
26 kJ
correct
Explanation:
m = 1.00 g
Δ
H
vap
.
= 2.26 kJ/g
q
=
2
.
26 kJ
g
¶
(1 g) = 2
.
26 kJ
002
(part 2 of 3) 10 points
What is
w
for this process?
1.
w
=

1
.
70 J
2.
w
=

1
.
70 L
·
atm
correct
3.
w
= +1
.
70 L
·
atm
4.
w
= +1
.
70 J
Explanation:
P
= 1 atm
T
= 100
◦
C + 273 = 373 K
density = 1 g/mL
W
=

P
Δ
V
V
i
= (1 g)
1 mL
1 g
¶
‡
1 L
1000 mL
·
= 0
.
001 L
V
f
=
n R T
P
=
0
.
082058 L
·
atm
1 mol
·
K
¶
373 K
atm
¶
×
(1 g)
1 mol
18 g
¶
= 1
.
701 L
w
=

(1 atm)(1
.
701

0
.
001) L
=

1
.
70 L
·
atm
003
(part 3 of 3) 10 points
What is Δ
E
for this process?
1.
Δ
E
= 2
.
43 kJ
2.
Δ
E
= 2
.
09 kJ
correct
3.
Δ
E
= 0
.
56 kJ
4.
Δ
E
= 1
.
29 kJ
Explanation:
Δ
E
=
q
+
w
= 2
.
26 kJ +
‡

1
.
70 L
·
atm
·
×
‡
101
.
33 J
L
·
atm
·‡
1 kJ
1000 J
·
= 2
.
09 kJ
004
(part 1 of 1) 10 points
Calculate the quantity of energy required to
change 3.00 mol of liquid water at 100
◦
C to
steam at 100
◦
C. The molar heat of vaporiza
tion of water is 40.6 kJ/mol.
1.
13.5 kJ
2.
40.6 kJ
3.
122 kJ
correct
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Killough, Ian – Homework 8 – Due: Nov 14 2006, 4:00 pm – Inst: Donna C Lyon
2
4.
None of these
5.
300 kJ
Explanation:
n
= 3.0 mol
40
.
6 kJ
mol
·
3 mol = 121
.
8 kJ
005
(part 1 of 1) 10 points
How much heat is required to vaporize 50.0
g of water if the initial temperature of the
water is 25.0
◦
C and the water is heated to
its boiling point where it is converted to
steam?
The specific heat capacity of water
is 4
.
18 J
·
(
◦
C)

1
·
g

1
and the standard en
thalpy of vaporization of water at its boiling
point is 40
.
7 kJ
·
mol

1
.
1.
23.5 kJ
2.
64.2 kJ
3.
40.7 kJ
4.
129 kJ
correct
5.
169 kJ
Explanation:
m
= 50 g
T
i
= 25
◦
C
T
f
= 100
◦
C
C
= 4
.
18 J
/
g
/
◦
C
Δ
H
vap
= 40
.
7 kJ/mol
H
=
m C
Δ
T
+
m
MM
Δ
H
vap
= (50 g) (4
.
18 J
/
g
/
◦
C)
×
(100

25)
◦
C
1 kJ
1000 J
+
50 g
18 g
/
mol
(40
.
7 kJ
/
mol)
= 128
.
731 kJ
006
(part 1 of 1) 10 points
Calculate the standard reaction enthalpy for
the reaction.
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 Spring '07
 Fakhreddine/Lyon
 Enthalpy, Donna C Lyon, Killough

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